Structural aircraft parts located in areas that are potentially exposed to flames need to be fire resistant under a regulatory obligation. The standards require minimum resistance for 15 minutes from a part exposed to a flame at 1100° C. combined with vertical vibration with 0.4 mm amplitude and 50 Hz frequency. “Fire resistance” qualification is defined by the achievement of different performance levels, which correspond to standards or the internal requirements of the aircraft manufacturer, namely:                no overrun of critical self-ignition temperatures of the structure during its degassing phase;        the temperature on the face of the structure opposite the face exposed to the flame may not exceed 500° C. after 5 minutes of exposure, and 700° C. after 10 minutes of exposure;        exposure to an energy flow of 120 kW*m−2 may not perforate the structure during the first 10 minutes of exposure.        
To that end, different protection techniques are used. The document EP 0167533 provides a view of the protection techniques of the prior art.
These different protection techniques of the prior art have the drawbacks of making a significant addition of mass, as the specific gravity of the protective means is greater than that of the structural part, and of not following the shape of the part. Further, the coverings used to protect the parts according to the methods of the prior art have the drawback of being sensitive to perforation and tearing, and such degradation of said covering leads to a loss of efficiency of the covering in respect of fire protection. In order to remedy that drawback, a solution of the prior art consists in protecting the thermal insulation with metal shells. Beyond the significant addition of mass resulting from this solution, the metal shell tends to deform and dilate thermally in a different way from the structure, which makes it difficult to fix it to said structure and results in significant mechanical constraints in the structure when the metal shell is exposed to a flame, or even during temperature variations that occur in service. 0.08 mm thick sheets of stainless steel are commonly used for that purpose. The mass added by these sheets is about 1.270 kg*m−2, while the fine thickness of said sheets only offers moderate mechanical protection to the underlying protective covering and is sensitive to perforation. Thus, when the underlying protective covering has a surface density of about 1 kg*m−2, the mass added by that protective solution of the prior art is about 2.270 kg*m−2.